Synthesis and X-ray Crystal Structures of Novel Spiro 1,3-benzoxazine Dimers

Abstract

Novel spiro 1,3-benzoxazine dimers are obtained when hydrazones of 2-hydroxyacetophenone are treated with triphosgene. An X-ray crystal structure, and the NMR and mass spectra of these new compounds, are reported and discussed.

Cyclization of Hydrazones of 2-Acetyl-1-naphthol and 1-Acetyl-2-naphthol with Triphosgene. Synthesis of Spiro Naphthoxazine Dimers

“…This might be speculated as a result of the orientation of the aromatic rings in respect to these positions, which needs further studies. In addition, the above results for compounds 17-19 are in close resemblance to these reported for the spiro 1,3-benzoxazine dimmers which might suggest that they have similar steric environment for the 1,3-benzoxazines [ 8 ].…”

“…For example, compound 18 shows in its EIMS spectra fragment peaks at m/z 505 and 489, arising from the loss of ClC 6 H 4 N 2 CO and ClC 6 H 4 N 2 CO 2 , respectively. This type of fragmentation was previously observed with analogous spiro compounds [ 8 , 9 ].…”

“…These results are in agreement with our previous reports on the reaction of hydrazones of 2-hydroxyacetophenones with triphosgene. It was observed then that the use of 0.5 equivalents of triphosgene gave the 4-methylene-1,3-benzoxazines, while the spiro 1,3-benzoxazine dimers were obtained when 1.0 equivalent of triphosgene was used [ 8 ]. The structures of those compounds were established based on X-ray crystal structure and spectroscopic studies [ 8 , 9 ].…”

“…It was observed then that the use of 0.5 equivalents of triphosgene gave the 4-methylene-1,3-benzoxazines, while the spiro 1,3-benzoxazine dimers were obtained when 1.0 equivalent of triphosgene was used [ 8 ]. The structures of those compounds were established based on X-ray crystal structure and spectroscopic studies [ 8 , 9 ]. As a result, we are showing here partial spectroscopic data for compounds 9-16 ( Table 3 and Table 4 ) and 17-20 ( Table 5 ).…”

“…Examples of important heterocyclic systems prepared using this reagent include benzothiadiazepines [ 1 ], quinazolines [ 2 ], diazolidines [ 3 ], imidiazolidines [ 4 ] and azetidines [ 5 ]. We have recently reported the use of triphosgene in the cyclization of hydrazones and Schiff bases of 2-hydroxy- and 2-aminoacetophenones to give 1,3-benzoxazines [ 6 , 7 ], spiro 1,3-benzoxazine dimmers [ 8 ], quinazolines and spiro quinazoline dimers [ 9 ].…”